Modulation of optical carriers using millimeter-wave signals are desired for telecommunications using fibre optics in order to achieve a wireless broadband service connection and distribution. The millimeter wave signal is desired to be phase coherent with the reference signals. A phase stable millimeter wave signal can be generated by electronic non-linear frequency multiplication of a low frequency reference signal. A phase stable millimeter wave can also be generated in the optical domain for wireless signal transmission using optical fibres. However, the process of generating the millimeter wave in the optical domain has the problem of stability because any small wavelength changes in the optical domain, is translated into a substantial frequency deviation in the electrical domain.
Many methods have been developed to generate millimeter waves, which include combining two laser outputs with frequency offset equal to the desired millimeter wave signal frequency as well as using two independent laser oscillators which are injection locked to different optical modes of a mode-locked laser (dual mode laser) and later combined to produce heterodyne output signals of millimeter wave. However, these techniques do not guarantee the production of a stable millimeter wave signal and are not tuneable for the user to choose the desired frequency for data transmission.
In view of the above limitations, it is desirable to provide a stable millimeter wave source while offering tuning capabilities in order for the users to choose the relevant frequency of choice for broadband wireless data transmission.